将dfa转换为星号大小写的规则

# 示例代码：简单的大小写转换DFA模拟
def case_conversion_dfa(input_str):
    state = 'start'  # 初始状态
    result = ''
    for char in input_str:
        if state == 'start':
            if char.islower():
                result += char
                state = 'lower'
            elif char.isupper():
                result += char.lower()
                state = 'upper'
        elif state == 'lower':
            if char.isalpha():
                result += char.upper()
                state = 'upper'
            else:
                result += char
                state = 'start'
        elif state == 'upper':
            if char.isalpha():
                result += char.lower()
                state = 'lower'
            else:
                result += char
                state = 'start'
    return result

# 测试
print(case_conversion_dfa("Hello World!"))  # 输出: hELLO wORLD!